The "Leaning Tower of Pisa" is famous for its 17 feet lean from the perpendicular, caused by the settling of its foundation. The third and last structure of the city’s cathedral complex was planned to stand 185 feet high, and was made of white marble. When the third story was completed, people noticed the uneven settling of the foundation. The engineer, Bonnano Pisano, compensated for the lean by making the remaining stories taller on the short side causing the structure to sink even further because of the extra masonry. There were several interruptions made during its construction, while engineers sought for solutions for the leaning tower. The foundations were strengthened by injecting cement grouting during the last century and in the 20th century the building has been in danger of collapsing. Currently engineers are considering different schemes to save the tower.